A good tube run tells you a lot about the tech who built it. Clean bends, square ends, and fittings that line up without forcing anything. A bad one has flattened bends, extra fittings where a bend should have been, and a tube that has to be pulled sideways to reach the port. After twenty years of building and fixing instrument lines, here is what I tell anyone learning to bend stainless tubing.
Bend Instead of Adding Fittings
Every fitting is a possible leak point. A smooth bend in place of an elbow and two connections means fewer places to check, fewer parts to stock, and less pressure drop. Bends also give a run some flex for vibration and thermal movement. When you plan a run, ask how many fittings you can replace with a bend.
Use the Right Bender for the Tube Size
Hand bending stainless, or using a bender made for a different OD, is how tubes get kinked and flattened. A bender sized for the tube supports the wall all the way around the bend and sets a consistent radius. We carry RIDGID tube benders in 1/4", 3/8" and 1/2" on our tools page.
Wall thickness matters too. Thin-wall tube is more likely to flatten or wrinkle on the inside of the bend. If you are unsure whether your tube and bender are a good match, ask before you start cutting good tubing.
Measure, Mark, and Plan the Sequence
Measure from the face of each port and mark the tube with a fine marker, not a scribe that can scratch the surface. Line the mark up with the reference marks on the bender every time. When a run has several bends, plan the order before you start. Working and measuring from left to right toward the other keeps small measuring errors from stacking up.
Leave enough straight tube at each end for the fitting. The tube has to go fully into the fitting body and bottom out straight. A bend that starts too close to the fitting will keep the tube from seating squarely, and that is a leak waiting to happen.
Bend Slow and Allow for Spring-Back
Use steady, even pressure. Jerking the handle is how you get wrinkles. Stainless springs back a little after you release the bender, so you will usually need to bend a few degrees past your target. Make a test bend on a scrap piece to see how your tube behaves, and check it against a square or protractor.
Inspect Every Bend
Look at the outside and inside of each bend. You want a round, smooth bend with no flat spots, kinks, or wrinkles. A flattened bend restricts flow and weakens the tube. If a bend is bad, cut it out and start over. A few feet of tubing costs less than a call-out for a leak or a potential accident.
Finish the Ends Right
Once your bends are set, cut to final length with a tube cutter made for stainless, like the RIDGID tube cutter. The GRIP-IT TOOL locks onto the tube while you cut so it does not spin in your hand. Then deburr inside and out with a deburring tool before the tube goes into a fitting. You can find all of these on our tools page, and we stock the 316/316L and 304/304L tubing to go with them on our tubing page.
We're Here to Help
If you are planning a run and want a second set of eyes on tube size, wall thickness, or the right bender, A-Best Industrial Inc. Fittings, Valves, and Tubing is glad to help. Call us at 310-833-3353 or email sales@abesttube.com, Monday through Friday, 8:00 AM to 5:00 PM Pacific, with after-hours emergency service available.